The hallmark of panic disorder is the occurrence of unpredictable, spontaneous episodes of intense anxiety termed panic attacks. Since, by their very nature, panic attacks are unpredictable, it is difficult to observe and study panic attacks at the actual point of panic. For this reason, pharmacological strategies were developed to facilitate the study of panic disorder, panic attacks, and their component features in a laboratory setting. In an effort to determine whether CCK systems may play a role in anxiety and anxiety disorders, studies are in progress to determine the effects of pentagastrin, a synthetic CCK agonist, in healthy volunteers, patients with panic disorder, and patients with social phobia. Intravenous administration of pentagastrin, a synthetic CCK agonist, leads to dose-related increases in anxiety and symptoms of panic attacks. Patients with panic disorder and social phobia are more sensitive to the effects of pentagastrin than healthy volunteers. When pentagastrin is administered in the context of a structured social interaction task, patients with panic disorder and social phobia report similar behavioral effects and have similar physiological responses.